Centrifugal fan.



A. J. BOWIE, JB. GBNTRIFUGAL FAN.

APPLICATION FILED JUNE 3,1905.

2 SHEETS-SHEET 1.

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2 SHEETS-SHEET 2.

Patented Jan. 19, 1909.

A. J. BOWIE, JR. GENTRIPUGAL PAN.

APPLIUATION FILED JUNE 3,1905.

f d y AUGUSTUS J. BOWIE, JR., OF WASHINGTON, DISTRICT OF COLUMBIA.

CENTRIFUGAL FAN.

Specification of Letters Ifatent.

Patented Jan. 19, 1909.

Application led June 3, 1905. Serial No. 263,567.

To all whom it may concern:

Be it known that I, AUGUSTUS J. Bowin, Jr., a citizen of the UnitedStates, residing at lVashington, District of Columbia, have inventedcertain new and useful Improvements in Centrifugal Fans; and I do herebydeclare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which 1tappertains to make and use the same.

The invention has reference to centrifugal fans or blowers, and has forits object to provide a machine of the character described, having itspartsso constructed and arranged as to avoid back slippage of air, tosubpress eddy currents within the casing, and to eliminate shock betweenthe entering air and the vanes; whereby the air is caused to circulaterapidly through'the machine withoutloss of energy due to abrupt changeof direction of How, or to violent impact With the moving parts of themachine, so that the mechanical efliciency of the machine is materiallyincreased.

In the accompanying drawings; Figure 1 is a vertical transverse sectionof a centrifugal fan embodying the features of my invention; Fig. 2 is aside elevation thereof, certain portions being broken away in order tomore clearly indicate the relative arrangement of the interior parts;Fig. 3 is a View corresponding to that in Fig. 1, illustrating amodified form of the invention; Fig. 4 is la side elevation of themachine shown in Fig. 3, the volute casing, however, being omitted; Fig.5 is a vertical transverse section of another modification, illustratinga suitable form of casing and of runner' and blades which may beemployed in fans of large size with sheet iron casings. Fics. G, 7 and 8are diagrams illustrative of the mode of constructing the suction orintake ends of the blades of the fan.

Considered generally, the apparatus comprises a casing a, into whichprojects power shaft L, having on its inner end a hub c, to which isbolted or otherwise attached a series of blades, designated by referenceletters d, d, and d, respectively, in the several modifications. Thecasing a is constructed of the usual volute form, with a constantlyincreasing section from the cutolf lip to the discharge. The centrallydisposed inlet is provided with a flaring or bell shaped mouth f toavoid loss of head in the entering air. This flaring intake f may,

of course, be located on the casing, or, if a suction pipe is used,- atthe inlet end of said pipe. ln Figs. 1, 2, 3 and 4 of the drawing, thebell shaped intake f is formed as part of an annular casting e, which isbolted to the front of the casing a. In order to avoid back slippage ofair at the intake, if the fan is of the closed runner ty e, a ring 7L,secured to the suction end o the runner, engages a groove g in the innerface of intake f', the ring and the groove being accurately turned toprovide a close fit having ust sufficient clearance laterally andcircumferentially to permit the ring to turn freely, without allowingreverse air currents to blow back into the bell f.

In Figs. 1 and 2, which illustrate a preferred construction employed infans with cast iron casings, the vanes are inclosed by conical orconoidal walls z', at front and back, which walls are attached to thevanes and form the lateral surfaces of the runner, being so constructedas to suppress eddy currents within the runner and to effecta gradualchange in the direction of flow of the air from the suction entrance tothe discharge end of the runner; that is to say, to gradually change thedirection of the current of air, moving axially of the fan at theentrance, to a substantially radial movement thereof at the point ofdischarge from the vanes of the runner. The relation and arrangement ofthe lateral walls z', j, with respect to the gradually tapering bladesof the runner'are such that the change of velocity of the air across asection substantially normal to the surface of said walls, is gradualand practically uniform from the suction entrance to the discharge fromthe runner, so that, generally considered, the radial discharge velocityof the air from the runner is somewhat less than the initial or entrancevelocity of the air thereto. The effect of this arrangement of theblades and the inclosing walls therefor, is to avoid the eddy currentloss due to unequal radial surface distribution of air, occasioned bythe comparatively low radial velocity of discharge from the runners infans as heretofore constructed and at the same time to avoid the lossdue to too high a radial velocity, caused by increasing the radialvelocity of discharge over the axial velocity at entrance to the runner.By observing these conditions, I have found, for example, that ascompared with standard fans or blowers, my fan will than half that ofsaid standard fans.

or'produced in the following' dicate a cy inder,

and return upon itself,

vlocity substantially exists,

deliver more air, although the width of the face of the blades at theiroutlet end is less This eect may perhaps be explained by theconsideration that in afan in which the velocity of discharge isconsiderably greater than the velocity of intake the air, instead ofpassing in a continuous body directly through the runners without eddycurrents, 1s allowed, by reason of the shape of the runner, to expandgreatly and furthermore to eddy thus giving rise t'o efiiciency losses.ln a fan in which the velocity of discharge is greater than the velocityof intake a compression of the air within the runner and a uselesschange in the vewhich also gives rise to etliciency losses. ln myimproved fan the point of greatest velocity is at the initial portion ofthe runner and from there the air expands gradually and uniformlythroughout the length of the runner and throughout the body of thevolute casing, expansion being slight and entirely gradual s0 that noeddy currents are set up and at the same time no useless compression orchange of velocity takes place.

- 1n centrifugal fans, as heretofore constructed, a comparatively largelossl of efficiency tering air upon the blades or runners, as the entireenergy of the repeated blows between the fan blades vand kthe incomingair is wasted. The present invention contemplates the provision ofspecially formed blades or varies to take in air without shock, wherebythis element of loss is eliminated, and the eliiciency of the fan iscorrespondingly increased. This highly important feature of theinvention is effected by constructing each blade so that it shall have apropeller shape, viz. a constant pitch at the induction end, whichgradually curves in the direction of rotation toward a positionsubstantially' parallel of the axis of the shaft at the discharge end ofthe blade. Considering both speed and capacity of the fan, therefore,the important point to be observed is to give the entrance line of thevanes' proper propeller shape, of the Vanes gradually, until they are.substantially parallel to the axis of rotation along theirperipheraledges, so that the air will be passed smoothly and gently into en-'gagement with the vanes at the suction end, an

grjadually changed -or diverted in itsdirection ofv radially intothervolute casing. The initial portion of the blade orvane, to meet vtheconditions hereinbefore referred to, is generated l manner.

:,Referrin to Figs. 6, 7 and 8, let A, B, in-

- concentric with the shaft of the fan, intersecting lthe Vane lbetweenthe center of the shaft b and the ring h; Fig. 6

@agace velocity of is due to the sudden impact of the er1-- and to curvethe remaining portions' How until it is dischargedshowing the parts inend elevation; Fig. 7 being the development of said cylinder showing theline A", B of intersection of the cylinder and the vane, B being a pointin the suction edge of the blade or vane;'and Fig. 8 being a radialprojection of the blade or vane. Let VA indicate the velocity anddirection of the entering air, and VF the peripheral velocity of thevane at the line of 1ntersection of the cylinder A B therewith, and VRthe resultant of VA and VF, then by making the inclination or curvatureof the edge of the vane at B tangent to the resultant of VA and -VF, theair entering yand engaging the vane at point B will not be subject toshock or impact blow, but will be advanced along the surface of the vanewithout resistance. As VF varies with the distance of point lB from theaxis, it is evident that the inclination or curvature of the initialportion of the blade must also vary, to

' meet the necessary condition that it shall be tangent to the resultantof the velocity of the entering air current and the circumferential theedge of the vane at every point in the latter taken negatively. ln otherwords, the blades or vanes shall have an initial curvature along theirsuction endsA such that the tangent to the line of intersection of avane and a cylinder concentric with the axis, will be along theresultant of the velocity of the entering air current, considered as onecomponent, andthe circum' ferential velocity of any particular point ofthe suction end in question taken negatively, considered as the othercomponent. As the values of VA and VF are known, or may be readilydetermined, it is evident that the proper initial curvature of thesuction ends of the vanes may befaccurately calculated, and the curveplotted therefrom, or said curve may be graphically determined byrepresentlng the velocities VA and VK as 1n Fig. 7, determining theresultant VR thereof for varying distances from the axis ofthd fan, andconstructing a curve which shall be tangent to these resultants, whichcurve will be coincident with the edge or suction endof the blade. x

As heretofore referred to, the portions of vL15 the blades or vanessucceeding the initial or suction ends thereof, are then graduallycurved so that they'tend to or: practically do become parallel withVVthe axis of the fan at their discharge ends. These `.features ofconstruction areclearly illustrated in Figs. 1

Aand 2, in which' .l indicates the suction ed e of the `blades or vanes,so curved, in accor v ,i ance with the rule hereinbefore enunciated,that the entering air engages .thesuction edges of the blades withoutshock, and the succeeding portions of said blades are gradually curveduntil. their discharge ends `or edges 2 are 'substantially parallel withthe axis of the fan, and the discharge of the air therefrom is in asubstantially radial direction. If desired, however, in addition to theinitial curvature ofthe vanes, they may be bent gradually either forwardor backward with reference to the direction of rotation, as may bestsubserve the conditions under which the fan is to be operated.

In centrifugal fans, as'heretofore constructed, considerable energy hasbeen lost, by reason of eddy currents, formed in the receiving chamberfor the air discharged from the fan. ln order to overcome thisdifficulty, which, as above noted, is inherent in smaller fans, lconstruct the volute casing a with outwardly inclined or flaring sides,which are closed by the curved cover, so that the air leaving theperipheral edges of the fan blades or vanes is discharged into a chamberconstantly increasing in width by reason of the flared sides, and indepth by reason of the volute form of the casing.

lt has been demonstrated, by tests, that fans having the characteristicstructure and relative arrangement hereinbefore described, take in airwith practically no loss of head, due to the flaring bell mouth lj, loseno air by back slippage, and are materially steadied in their rotationby reason of the ring /i snugly iitting the groove g in the end of thebell f', eliminate eddy currents within the casing and produce a gradualchange of the direction of the air currents through the gradually curvedlateral walls 2' and j, and also produce an increased ethciency byvirtue of the velocity of the radial discharge from the vanes being lessthan the velocity at the suction or intake, avoid eddy current losses inthe volute because of the gradually mcreasingfcross sectional area ofthe volute chamber, and, lastly, take in air without shock and transmitit along the channels between the blades with practically no loss ofenergy by reason of the particular shape or curvature of the initialportion of said blades, andthe gradually curved surfaces'of said bladestoward parallelism with the axis of the fan.

For constructive reasons, it may be found advisable at times to form theblades or vanes'without the initial curvature at the suction or entranceend thereof, but to preserve all of the other characteristic features ofthe fan, as hereinbefore described. Under such conditions, means shouldbe provided to deliver the air from the suction bell f to the surfacesof the vanes or blades 'without shock or impact blow, or, in otherwords, to deliver the inliowing current to the blades, so that the airwill be received by the latter and conveyed to the substantially radialdischarge end thereof without loss due to shock or sudden change ofdirection. Such a construction is illustrated in Figs. 3 and 4, in whichthe fan proper has the essential characteristics of that hereinbefore described, except that the blades or vanes d are located in substantiallyradial planes. Vithin the throat of the bell f, however, there islocated a series of stationary guide vanes m each having one edgeattached to a central axis n, and the opposite edge attached to aninclosing ring o fitted closely within the bell. These vanes m havetheir front edge substantially normal to the axis n, but are given atwist or curvature both longitudinally and transversely, so that theinner edge next to the suction end of the blades d has an inclination orcurvature similar to the edge Z of the blades d in Figs. l and 2,whereby the tangential component of the air velocity leaving the vanes mand entering upon the vanes or runners d', is just equal, at all pointsof the rotation, to the velocity of rotation of the corresponding pointsof the vanes or runners al. lt will thus be apparent that the aircurrents taken in by this type of fan, will be given the necessarydirection and the requisite velocity to be taken up by the vanes orrunners al without shock or impact blow.

ln the larger types of fans, it is found preferable, for constructivereasons, to modify the character of the discharge chamber or volute, andalso of the runner, as illustrated in Fig. 5, in which construction,however, the other essential characteristics of the fan illustrated in`Figs. l 'and 2, are preserved. lt will be noted that this fan has theflaring bell mouth f, the initially curved blades d being constructedand arranged to take the air without shock and discharge the same in asubstantially radial direction into the chamber it" of the volute. Theblades or runners It are inclosed by lateral walls z" and j', attachedto and rotating therewith, the wall z" being formed partly by theextended conical walls of the hub and partly by a peripheral ring. Thevolute It" is made of substantially rectangular cross section, as shownin liig. 5, increasing gradually toward "the ultimate discharge Z.

To avoid eddy currents, the peripheral edges of the runner enter thedischarge chamber la so as practically to close the receiving chamberfrom the iest of the casing.

Although the centrifugal fans herein before described, are of the closedruimer type, it is to be understood that the invention is not limitedthereto, as its main characterist-ic advantages may berealized in openrunner fans in which the lateral walls z', j, are fixed to the casing,and the blades revolve within said walls, with small running clearance.

Having thus described my inventiomwhat l claim and desire to secure byLetters Patent, is

fil. ln a centrifugal fan, the combination o an inclosing casingprovided with an air of that point in the edge of the fan blade Ycomponent, substantially c lateral surfaces structed and arranged as toform passages fcurved beyond the inlet or suction opening, and a seriesof rotary blades Whose Suction ends have an initial curvature such thatthe liney of intersection of a vane and a cylinder concentric with theaxis has, at the point Where the line of intersection cuts the edge ofthe ,fan blade, a tangent which coincides in direction Witli theresultant of the velocity of the entering air current, considered as onecomonent, and the circumferential velocity taken negatively, consideredas the other as described.,

2. In a centrifugal fan, the combination of an inclosing casing providedwith an air inlet or suction opening, and a series of rotary bladesWhose suction ends have an initial curvature such thatv-the line ofintersection of a vane and a cylinder concentric with' the axis has, atthe point Where the line of intersection cuts the edge of the fan blade,a tangent Which coincides in direction With the resultant of thevelocityof the entering air current, considered as one component, and thecircumferential velocity of that point in the edge of the fan bladetaken negatively, considered as the other component, the blades beinglfurther gradually curved beyond the point of initial curvature untiltheir discharge ends merge into planes substantially parallel to theanis, substantially as described 3. ln a centrifugal fan, thecombination of an inclosing casing provided with an air inlet or suctionopening, and a Yseries of rotary blades Whose suction ends have aninitial curvature such that the line of intersectign of a vane and iWith the axis has, at the point Where the line of intersection cuts theedge of the fan blade, a tangent which coincides in the resultant of thevelocity of the entering `air current, considered as one component,

and the Vcircumferential velocity of that point in the edge of the fanblade taken negatively, considered as the other component, the bladesbeing further gradually point of initial curvature until their dischargeends merge into planes substantially parallel to the axis and alsoradial to said axis, substantially as described.

4. ln a centrifugal fan, the combination of an inclosing casing providedwith an air inlet or suction opening, a series of rotary bladesoperating in the casing, and confining for said blades, all so confromthe point of intake to the point of discharge from the blades in whichpassages the cross-sectional area normal to theaxis of the passagegradually and uniformly increases from the point of intake to the pointof discharge to such an extent'that the velocity of discharge is onlyslightly less a cy-linder concentric Y direction with than Y ceases thevelocity ofintake whereby unequal radial distribution and eddy currentlosses are avoided, substantially as described.

5. ln a centrifugal fan, the combination l of an inclosing casingprovided With an air inlet or suction opening, av series of rotaryblades operating in the casing, and confining lateral surfaces for saidblades, all so constructed and arranged as to form passages from thepoint of intake to the point of discharge from the blades in whichpassages i the cross-sectional area normal to the axis of the passagegradually and uniformly increases from the point of intake to the pointof discharge to such an extent that the velocity of discharge in onlyslightly less than the velocity of intake, whereby unequal radialdistribution and eddy current losses are avoided, the said lateralsurfaces being gradually curved to effect a gradual change in thedirection of flow of the air, substantially as described.

6. ln a centrifugal fan, the combination of an inclosing casing providedWith an air inlet or suction opening, a series of rotary bladesoperating in the casing, and conning lateral surfaces lfor such blades,all so constructed vand arranged as to form passages from the point ofintake to the point of discharge from the blades in which passages thecross-sectional area normal to the axis of the passage gradually anduniformly increases from the point of intake to the point of discharge,to such an extent that the `vvelocity the velocity of intake, incombination with an outer portion of the casing constituting a receivingchamber and having a gradua ly increasing cross-sectional. area from thedischarge edges of the blades to the outer Wall of the casingsubstantially as described.

7.. ln a centrifugal fan, the combination of an inclosing casingprovided with an air inlet or suction opening, a series of rotary bladesoperating in structed and arranged as toform passages from the point ofintake to the point of disthe cross-sectional area normal to the axis ofthe passage gradually and uniformly increases from the point of intaketo the point of discharge, to such an extent that the velocity ofdischarge is only slightly less than. the velocity of intake, incombination with an outer volute portion of the casing constitut'ing areceiving chamber and having a gradually from'the discharge edge of theblades to the outer Wall of the casing; substantially as described.

8. In a centrifugal fan,

air inletV or suction opening, of air passages of discharge is onlyslightlyless thanlateral surfaces for such blades, all so conchargefrom. the blades in Which passages the casing, and conining increasingcross-sectional area` the combinatin with an inclosing casing providedvvith'an,

i communicating with the suction opening and formed in art by a seriesofprotary blades, the initial) portions of said passages having acurvature such that if a line be drawn from any point on the line ofintersection of the initial portion of a fan blade with a cylinderconcentric with the axis and equal in amount and direction to thecircumferential velocity of that point in thel fan blade, then the lineclosing the triangle thus formed Will coincide in direction and amountwith the velocity of the entering air, substantially as described. Y

9. iin a centrifugal fan, the combination with an inclosing casingprovided with an air inlet or suction openlng, of air passagescommunicating with the suction opening and extending through theinclosing casing and formed in part by a series o rotary blades whosesuction ends have an initial curvature such that the line ofintersection of a Vane and a cylinder concentric With the axis has, atthe point where the line of intersection cuts the edge of the fan blade,a tangent Which coincides in direction with the resultant of thevelocity of the air current entering upon the blades from the initialportions of the passages considered as one component and thecircumferential velocity of that point in the fan blade takennegatively, considered as the other component, substantially asdescribed.

in testimony whereof I ax my signature, in presence of two Witnesses.

AUGUSTUS J. BOVE, JR. Witnesses:

Jorm C. PENNIE, J., E, HUTCHINSON, Jr.

